The control of insects was one of the first problems undertaken by agricultural chemical research, and continues to be pursued vigorously by the art. Insects of many orders assault crops of all types, and also cause unsanitary conditions and nuisance by contaminating foodstuffs. The damage caused by insects is incalculable, and the control of harmful insects necessarily is of the highest priority.
Recently, the search for new and better insecticides has been spurred by the withdrawal from use of the old residual insecticides.
The compounds of this invention are new to organic chemistry. Some items in the prior art, however, are of interest. For example, Cebalo, U.S. Patent 3,726,892, discloses herbicidal 1,3,4-thiadiazol-2-ylureas.
Rao, Indian J. Chem. 8, 509-13 (1970), teaches a synthesis method for 2-amino-1,3,4-thiadiazoles, which are intermediates for the compounds of this invention.
Wellinga and Mulder, U.S. Pat. No. 3,748,356, show herbicidal and insecticidal efficacy of N-benzoyl-N'-phenylureas.